Process for regenerating manganese oxide acceptors for hydrogen sulfide



Au fzo, 1963 x m EXPRESSION .Oi'ginal Filed Feb. 13, 1958 2 Sheets-Sheet1 HIGH SULFUR NET CARBONACEOUS FLUE GAS GAS soLms AND so T u 20REGENERATED 4X 2 ACCEPTOR DESULFURIZATIO'NY REGENERATION l7 la l6SULFIDED '9 g I ACCEPTOR LOW SULFUR AIR CARBONACEOUS souos 40 50 so 10e0 90 I00 OF MnS REGENERATED v INVENTORS- .1. D. BATCHELOR ETEAL PROCESSFOR REGENERATING MANGANESE OXIDE ACCEPTORS FOR HYDROGEN SULFIDE JAMES D.BATCHELOR GEORGE P. CURRAN EVERETT GORIN TORNEY D. BATCHELOR a-rALPROCESS FOR REGENERATING MAN 3 0 1 0 3 E D I X 0 E S m. m

Aug. 20, 1963 ACCEPTORS FOR HYDROGEN SULFIDE Original Filed Feb. 13,1958 2 Sheets-Sheetv 2 TIME MINUTES XMnO 0 Mn O TIME MINUTES .0. -7-v wa O n ./M 02 1% mm s N n v M W ,4E .M T 2 O O O O O O O O O 0 8 6 4 2 86 4 2 INVENTORS R v O LN M N RI 7 CRR v| 0 7 E B v R w Tv O 7 3 s ERR AM0 na Y B United States Patent 3,101,303 PROCESS FOR REGENERATENGMANGANESE OXIDE ACCEPTQRS FUR HYDROGEN SUlLlFiDE James D. Batchelor,Springfield, Va., and George P. Curran and Everett Gorin, Pittsburgh,Pa, assiguors to Consolidation Coal Company, Pittsburgh, Pa, acorporation of Pennsylvania Continuation of application Ser. No.715,136, Feb. 13, 1958. This application Apr. 29, 1960, Ser. No. 26,9277 Claims. (Cl. 2023l) The present invention relates to a process forregenerating manganese oxide acceptors for hydrogen sulfide. Moreparticularly, it relates to a process for removing sulfur contaminationfrom carbonaceous solid materials by treatment with hydrogen in thepresence of manganese oxide-type solid acceptors for hydrogen sulfide.

Such sulfur removal processes for carbonaceous solid fuels have beendescribed in copending U.S. patent application S.N. 527,705, now US.Patent 2,824,047, filed August 11, 1955, by Everett Gorin', George P.Curran and James D. Batchelor, assigned to the assignee of the presentinvention. A further process relating to sulfur removal and calcining ofcarbonaceous solid fuel briquets has been described in copending US.patent application S.N. 635,278, since abandoned, filed January 22,1957, by James D. Batchelor, Everett Gorin, George P. Curran and RobertJ. Friedrich, assigned to the assignee of the present invention.

The presence of sulfur in carbonaceous solid fuels limits their use inmetallurgicalapplications. Accordingly, most metallurgical fuels areobtained by employing low sulfur content starting materials, e.g., lowsulfur coal is converted to low sulfur metallurgical coke. Sulfurremoval processes of the typedescribed in the aforemen tioned patentapplications permit the use of high sulfur content fuels as startingmaterials for preparing low sulfur content carbonaceous fuels formetallurgical use. For example, the sulfur removal process may beprovided as a treatment for the solid residue (termed char) resultingfrom low temperature carbonization of bituminous coal. Where fluidizedlow temperature carbonization processes are used, the finely divided,low density, porous char productis particularly amenable to thosedesulfurization treatments. The desulfurization treatment can be appliedto any non-caking carbonaceous solid fuel such as cokes and chars. Cokefrom coal and hydrocarbonaceous residues (pitch coke), coke breeze, andlow temperature carbonization' char from coal and lignite are exemplary.The processes cannot be applied to caking carbonaceous solid fuels suchas caking coal since the thermal treatment encompassed in such processeswould cause these materials to become sticky and form coked masses whichwould bind the acceptor solids, thus preventing their recovery for reusein the process. Further the resulting coke would be contaminated withthe acceptor solids. Any sulfur transferred from the carbonaceous fuelsto the bound acceptor solids would remain in the solid coke. Theprocesses, however, are applicable to the desulfurization ofcarbonaceous briquets which may contain caking coal inter alia providedthe thermal treat ment is conducted to avoid severe caking andaccompanyiug formation of large coke masses.

In the aforementioned copending application S.N. 527,705 solidcarbonized carbonaceous fuels are desulfurized by treatment at elevatedtemperatures in the presence of hydrogen and a solid acceptor forhydrogen sulfide. A preferred acceptor in this process is one containingmanganese oxide. Examples of manganese oxide acceptors include particlesof substantially pure manganese oxide, inert supports such as silica,alumina and silicaalumina impregnated with manganese oxide, and highthree forms.

, 3,101,303 .Patented Aug.- 20, 1963:

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manganese content naturally occurring ores having a low content ofsilica-alumina, calcium and iron. The natu rally occurring ores are morefully describedin our copending application SerialNo. 715,058, now-US.Patent 2,950,231, filed February 13, 1958, by James D. Batchelor,"George P. Curran and Everett Gorin entitled Manganese Ore Acceptors forHydrogen Sulfide. A preferred inert support is mullite which comprisesabout to percent alumina and the balance silica.

According to the process of US. Patent 2,824,047, carbonaceous solidfuels containing sulfur are mixed with a solid material (termed anacceptor) which is capable of absorbing hydrogen sulfide. The mixture istreated with hydrogen gas at a temperature above about 1100 F. wherebythe hydrogen gas combines with the contaminating sulfur to form hydrogensulfide; the hydrogen sulfide is absorbed in situ by the acceptor. Sincethe hydrogen sulfide is absorbed instantly upon formation, there is onlya negligible paitial pressure of hydrogen sulfide in the desnlfurizationzone for inhibiting the reactions whereby sulfur is removed from thecarbonaceous solid fuels. The reaction mixture of solids is separatedinto (a) product desulfurized carbonaceous solid fuels and (b) the solidacceptor containing accepted sulfur. The acceptor may be regenerated andheated by contact with [air to restore its hydrogen sulfide acceptorproperties through elimination of previously absorbed sulfur. The heatedregenerated acceptor, when mixed with relatively cool carbonaceous solidfuels preferably provides the heat necessary to raise the solidsreaction mixture to a desulfurization temperature.

Where the sulfur-containing carbonaceous solid fuel is in the form offinely divided particles (e.g., fluidized low temperature carbonizationchar, petroleum coke and the like), the acceptor preferably is larger insize to facilitate separation'of desulfurized fuel from the sulfidedacceptor. When the sulfur-containing carbonaceous solid fuel is in theform of relatively large agglomerate masses, such as briquets, theacceptor preferably is in the form of finely divided fluidizable sizeparticles to improve contacting efficiency and to facilitate separationof desulfurized fuel from the sulfided acceptor.

carbonaceous solid fuels contain sulfur in at least Some of the sulfurexists as readily removable sulfur Which is organically bound in thecarbonaceous fuel. This, organically bound sulfur can be removed fromthe carbonaceous solid fuels rather easily by contact with hydrogen. Ifthe readily removable, organically bound sulfur is represented as C=S,the desulfurization reaction may be represented as follows:

carbonaceous solid fuel with pure hydro-gen gas. The

reaction (assuming iron sulfide) is as follows:

FeS+H H S+Fe The equilibrium ratio for-this reaction His/H is very low.Hence small quanties of hydrogen. sulfide in the gas phase will inhibitthe transfer of sulfur from the solid to the gas. At 1350 F., for exarnple,0.l2 volume percent of hydrogen sulfide in the hydrogen gas is theequilibrium value. At 1600 F., 0.28 volume percent of hydrogen sulfidein the hydrogen gas is the equilibrium value. Thus in order to removeinorganically, bound sulfur effectively, the ratio of H S/H must bemaintained at an extremely low value,-i.e., nearly pure hydrogen must beused. 7

A further type of sulfur existing in the solid carbonaceous fuels'isidentified as difiicultly removable sul- 3 fur which is principallyorganically bound. This type of sulfur exists in the form of refractoryorganic material and various inorganic sulfides. While this sulfurtheoretically can the removed by treatment of the carbonaceous solidfuels with pure hydrogen gas, nevertheless, even minutetraces ofhydrogen sulfide are sulficient to inhibit the transter of sulfur fromthe solids to the gas. Removal of the difiicultly removable sulfur isnot practicable under feasible processing conditions.

The ultimate desulfurization which can be achieved at any temperaturedepends upon the ratio of H s/H in the treating gases without regard tothe absolute pressure of the reaction system. While greater absolutepressure increases the rate of desulfurization, it does not aifect theultimate level of sulfur in the treated solids. In accordance with thesefindings, satisfactory desulfurization rates may be achieved attemperatures above about 1100 F. with atmospheric pressure. Higherpressure accomplishes the same desulfur'ization in shorter time. Apreferred pressure range for the desulfurization is about 1 to 6atmospheres absolute.

It is possible to maintain a low value for the ratio H s/H by employingenormous quantities of hydrogen as a treating gas. For example, the useof 1000 molar volumes of pure hydrogn gas in removing one mol of sulfurwould create an environment containing 0.10 volume percent of H 8 in HAlternatively, the ratio H s/H may be maintained at a low value byremoving the H 8 from the vapor state as quickly as it is formed. Theremoval of H from the vapor state can be accomplished by providing in adesulfurization zone a solid acceptor which has a greater afiinity forhydrogen sulfide than those materials with which the sulfur is bound inthe carbonaceous solid fuels. A preferred solid acceptor is onecontaining manganese oxide.

Throughout the specification, the term manganese oxide refers tocompounds containing manganese and oxygen, such as MnO, Mn O Mn O MnOwhich compounds are principally in the form of MnO. The term higheroxides of manganese refers to compounds containing more than one atom ofoxygen per atom of mantganese, e.g., Mn O Mn O MnO The reaction of themanganese oxide in the desulfurization treatment is as follows:

Thus the manganese oxide combines with the generated hydrogen sulfide toform manganese sulfide thereby removing from the vapor phase thehydrogen sulfide formed by desulfurization of the carbonaceous solidfuel.

Following sufiicient desulfurizing treatment of the carbonaceous sol-idfuels, the desulfurized fuels are separated from the solid acceptor andrecovered as a low sulfur carbonaceous fuel product. As such, the lowsulfur carbonaceous solid fuels are suitable for use as metallurgicalfuels.

The separated sulfided acceptor is regenerated by treatment with air torestore the manganese oxide for reuse as follows:

Thus in the overall process, the sulfur removed from the carbonaceoussolid fuels is rejected from the system in the form of sulfur dioxide.So much of the process has been more fully described in theaforementioned application, S.N. 527,705.

The use of H 5 acceptors has been'briefly described in relation todesulfunization processes for carbonaceous solid fuels. Such H 8acceptors also can be used for removing H 5 from any gas stream,regardless of source. For example, elimination of 1-1 8 from petroleumrefinery gases, pipeline gas, and the like can be accomplished bypassing the gases over an H S-accepto-r containing manganese oxide. TheH 8 will be absorbed by the acceptor and the manganese oxide convertedto manganese sulfide.

w The sulfided acceptor can be regenerated by treatment with air torelease sulfur dioxide and restore the manganese oxide.

The phrase H sabsorbing conditions as employed in this specificationrefers to a non-oxidizing environment containing H S at temperaturesWhere a favorable equilibrium exists for the reaction The preferredtemperature range for H s-absorbing conditions is about 1100 to 16 00"F. The ability of an acceptor to react with H 8 under H S-ahsorbingconditions is an important determinant in the efficiency of thefundamental desulfurization process.

Undesirable over-oxidation may accompany the regeneration whereby higheroxides of manganese are produced, for example, Mn O and Mn O Thepresence of these higher oxides of manganese is deleterious for tWoreasons.

First, the higher oxides of manganese are reduced immediately uponreturn to the desulfurization zone by reacting with hydrogen gastherein.

M11304 Mn O -l-H 2MnO+H O Consumption of valuable hydrogen in thismanner is inefiicient since there is no accompanying desulfurization.

Second, the reduction of these higher oxides of manganese produce watervapor which tends to suppress the H 3 absorption reaction.

The reaction equilibrium for the H 8 absorption is a function of pH O/ HS. Extraneous water vapor in the system will limit the rate of H 5absorption.

The object of the present invention is to minimize the productiono-fhigher oxides of manganese in the acceptor regeneration treatment.

According to the present invention, a portion of the MnS in the acceptoris allowed to remain in the acceptor throughout the regenerationtreatment. By allowing about 2 to 15 percent of the manganese to remainin the form of MnS, the yield of MnO is unexpectedly selective to thesubstantial exclusion of the undesirable higher oxides of manganese. Theresidual MnS does not affect the subsequent H S absorption properties ofthe acceptor since the MnS passes through the desulfurization zoneunchanged.

In the preferred embodiment, the acceptor is used not only to remove H Sfrom the vapor in the desulufurization zone but also to provide the heatrequirements for raising the temperature of the carbonaceous solids(undergoing desulfurization) to the desired desulfurization temperature.Thus there exists an overwhelming stioohiometric excess of MnO in thedesulfurization zone, dictated by the heat balance requirements.

For a full understanding of the present invention, its objects andadvantages, reference should be had to the following detaileddescription and accompanying drawings in which:

IGURE 1 is a schematic flow diagram illustrating a desulfurizationprocess for carbonaceous solid fuels employing solid acceptors \forhydrogen sulfide;

FIGURE 2 is a graphical illustration of the state of oxidation of themanganese oxide acceptor according to the extent of sulfur removal inthe regeneration zone; and

FIGURE 3 is a graphical illustration of the manner in which theregenerating oxygen is distributed among three competing reactions inthe regeneration zone.

The generalized flow sheet of FIGURE 1 illustrates the manner in whichan acceptor desulfiurization process can he carried cutin a continuousmanner. A desulfurization zone It) receives non-caking carbonaceoussolids containing sulfur through a conduit 11 and regenerated acceptorsolids through a conduit 12. In this instance, the

hydrogen gas, are autogenously produced through devolatilization of thecarbonaceous solids at the elevated temperature of the desulfurizationzone 10. Under preferred operating conditions the autogenously produceddevolatilization gases will be in sufiicient quantity to provide thefull hydrogen requirements for desulfurization so that extrinsichydrogen production is not required.

The desulfurization zone 10 is maintained at a temperature from about1100 to about 1600 F. Belowv about 1100 F., the desulfurization rate islow. Operation above about 1600 F. requires excessive heat and alsopromotes rapid deactivation of the acceptor. The pressure levelpreferably is high enough to provide a 'hydrogen gas partial pressure ofat least one atmosphere. A total pressure of from one to six atmospheresis preferred.

A t pical char (containing sulfur) produced by fluidized carbonizationof Pittsburgh Seam coal at 950 yields devolatilization gases containing58.6 percent hydrogen and 24.8 percent methane at 1.3 atmospheres and1350 F. The same char yields devolatilization gases 5 containing 48.7percent hydrogen and 32.9 percent methane at 3 atmospheres and 1350 F.

During passage through the des-ulfurization zone 10,

the treating gases remove sulfur from the carbonaceous solid fuels.

forming hydrogen sulfide.

The H S, upon formation, is at once absorbed by the solid acceptor andremoved from the gas phase.

furization desired. It must be borne in mind that theultimate sulfurlevel of the product is determined by the level of H 5 concentrationwhich the managnese oxide will maintain. Where the hydrogen partialpressure of the treating gases is about one atmosphere or greater,

satisfactory desulfurization can be achieved by subjecting 5 thecarbonaceous solids to the desulfurization conditions for a period ofabout three hours or less. Increased absolute pressure, as alreadypointed out, promotes more rapid desulfurization.

Desulfurized carbonaceous solids are removed from the desulfurizationzone 10 as product through a conduit 16.. Sulfided acceptor is removedthrough a conduit 17 and passed to an acceptor regeneration zone 18. Airis introduced into the regeneration zone 18 through a conduit 19 toraise the temperature of the acceptor through combustion of su fur alongwith a portion of the carbonaceous solids commingled therewith and toremove sulfur; therefirom through oxidation to sulfur dioxide.

MnS+%O MnO+SO +heat The temperature within the regeneration zone 18 ismaintained at about 1300 to 1800 F. Hot flue gases containing sulfurdioxide are removed from the regenerationzone"v 13 through a conduit 20.

Excessive oxidation in the regeneration zone 18 will result in theconversion of some MnO to higher oxides of. manganese as described.According to the present invention, the residence time and oxygen inputrate are regulated to restrict the oxidation such that from about 2,

to about 15 percent of the available manganese remains 6 in the vform ofMnS. The two-mentioned variables are regulated such that the amount ofoxygen introduced is within about 20 percent of that stoichiometricallydetermined for complete oxidation of all the MnS entering theregeneration zone 18. Substantially complete COHSUITIP-e tion of theintroduced oxygen will occur. This oxygen in part is consumed by thedesired reaction MnS-1 7 0 MnO-l-SO -l-heat and in part throughcombustion of carbonaceous, solids to provide the heat requirements forthe process and also in part to produce the undesirable higher oxides ofmanganese I 3MI1O+1/2O2+MI13O4.

ZMnO /2 0 Mn O Regenerated acceptor is returned to the desulfurizatiouzone 10 through the conduit 12 without deliberate cooling 0 v to servetherein as a means for removing H 8 therefrom and to supply the heatrequirements thereof.

To illustrate the unexpected results accruing from the practiceo-f thepresent invention, an introductory explanation of the terminology willbe helpful. In considering a mixture of various oxides of manganese(MnO, Mn O M11 0 for example) the ratio of oxygen to manganese can becalculated and the mixture can be identified by the empirical formula:MnO Where x is the calculated ratio.

If all the manganese exists as MnO, the value of x is 1.00. If all themanganese exists as Mn O the value of x is 1.33. If all the manganeseexists as M11 0 the value of x is 1.50. By this system ofrepresentation, it is apparent that the desired value of x in theempirical expression for the oxides of manganese should approximate 1.00for a regenerated acceptor entering the desulfurization zone.

Referring to FIGURE 2, the value of x in the expression MnO has beengraphically presented as a function of the percentage of MnS which isoxidized during regeneration in air. To develop the curve of FIGURE 2, asulfided acceptor was exposed to oxygen in a fluidized 'bed at 1700 F.The specific acceptor was a substantially pure screened fraction ofmanganese oxide. The

material was prepared by decomposing manganese nitrate to manganeseoxide. .The manganese oxide was briquetted, calcined, crushed andscreened. Samples of the acceptor were drawn periodically for analysis.About 60 percent of the available manganese was in the (form of MnS whenregeneration was commenced. The associated carbon was finely dividedparticles of pitch coke.

From FIGURE 2, it is seen that the yield of higher oxides of manganeseis negligible until the last portion of the MnS begins to oxidize, asevidenced by the value of x in the expression MnO 'The value of x doesnot rise above 1.01 until about 90 percent of the MnS has been oxidized.Thereafter the value of x increases markedly as the residual. M113 isoxidized. Hence it appears that formation of significant quantities ofhigher oxides of O manganese can be avoided by allowing a portion of theMnS to remain on the acceptor during the regeneration treatment.

For a further illustration of the present inventionpthe curves of FIGURE3 present graphically the distribution of oxygen entering a batch-wiseacceptor regeneration zone as a function of time. A specific acceptorwas the same substantially pure material described in connection withFIGURE 2. Initially the sulfided acceptor contained about 60 percent ofits manganese as MnS. Some finely divided pitch coke particles werecomrningled with.

the sulfided acceptor. Air was passed through the acceptor-coke mixtureas a fluidizing gas.

About percent of the initial oxygen reacts with the MnS to form MnO.exclusively; the remainder of the initial oxygen reacts with carbon fromthe coke to supply heat; none of the initial oxygen reacts with MnO toform higher oxides of manganese. Following about five minutes treatmentat a constant air input rate, only a minor portion of entering airreacts with MnS. The bulk of the air is used in the carbon combustionreaction. A significant portion of the air is consumed in formingundesirable higher oxides of manganese from the MnO already produced.Regeneration treatment extending beyond about five minutes (at the airinput rate used to develop the curves of FIGURE 3) would result only ina slight decrease of the MnS content of the acceptor at the expense of asignificant increase in the content of undesirable higher oxides ofmanganese.

The cross hatched area under the curves of FIGURE 3 corresponds to thecumulative amount of oxygen consumed in each of the three competingreactions. Continuing the regeneration treatment beyond about fiveminutes would produce more higher oxides of manganese than MnO (fromNnS) under the conditions employed for obtaining the data to develop thecurves of FIGURE 3.

The exact cut-off point for the regeneration will vary according to therelative oxygen-to-sulfided acceptor flow rate. However, a satisfactorycut-off will be achieved when from about 2 to about 15 percent of theMnS on the sulfidedacceptor is allowed to remain on the regeneratedacceptor. The utilization of oxygen in the regeneration process will benearly quantitative, i.e., substantially all of the oxygen introducedwill be consumed. Accordingly, the quantity of oxygen should be withinabout twenty percent of that determined stoichiometrically for reactingwith all of the available MnS.

The temperature range for the regeneration is from about 1300 to 1800 F,preferably from about 1300 to 1600 F. Where the acceptor comprises aninert support such as silica-alumina, silica or alumnia impregnated withmanganese oxide, regeneration should be conducted at a relatively lowtemperature within the range. Elevated temperature treatment ofsupported acceptor promotes deactivation of the manganese as describedin our copending applications S.N. 692,865, now U.S. Patent 2,927,063,filed October 28, 1957; SN. 692,897, now US. Patent 2,950,229, filedOctober 28, 1957; and S.N. 695,467, now US. Patent 2,950,230, filedNovember 8, 1957. Regeneration of high manganese content acceptorspreferably is conducted at somewhat higher temperatures within the range1300 to 1800 F. High manganese content acceptors include those preparedfrom substantially pure manganse oxide as well as those comprisingnaturally occurring manganese ores as set forth in copending applicationSrN. 715,058, now US. Patent 2,950,231, filed by us February 13, 1958.

The present process can be applied to advantage in an cyclicdesulfurization process employing manganese oxide acceptors and alsoemploying hydrogen gas as the sulfur transferring medium. Gaseousstreams and vaporized sulfur-containing liquids can be desulfurized aswell as the carbonaceous solid fuels herein described.

According to the provisions of the patent statutes, we have explainedthe principle, preferred construction, and mode of operation of ourinvention and have illustrated and described what we now consider torepresent its best embodiment. However, we desire to have it understoodthat, within the scope of the appended claims, the invention may bepracticed otherwise than as specifically illustrated and described.

This application is a continuation of our application Serial No.715,136, now abandoned, filed February 13, 1958.

We claim:

1. in a process employing solid acceptors containing manganese oxide forabsorbing hydrogen sulfide at temperatures above about 1100 F. to formmanganese sulfide, followed by oxidizing the manganese sulfide tomanganese oxide by reaction with oxygen, wherein undesired higher oxidesof manganese are formed, in said lastmentioned step the improvementwhich minimizes formation of said higher oxides, comprising controllablyoxidizing only about to 98 percent of the sulfide sulfur in saidsulfided acceptors so as to maintain about 2 to 15 percent of themanganese in the form of MnS, whereby a major portion of the manganeseis in the form of MnO and formation of higher oxides of manganese isminimized, and recovering the thus-treated regenerated acceptors forreuse under H s-absorbing conditions.

2. The improvement of claim 1 wherein the solid acceptor comprises amanganese-oxide impregnated inert support which is an oxide selectedfrom the class consis ing of silica, alumina and silica-alumina and theregeneration temperature is between 1300 and l600 3. The improvement ofclaim 2 wherein the inert support comprises mullite.

4. The improvement of claim 1 wherein the solid acceptor comprisessubstantially pure manganese oxidev 5. The improvement of claim 1wherein the solid acceptor comprises particles of naturally occurringhigh manganese content ore.

6. In a process employing solid acceptors containing manganese oxide forabsorbing hydrogen sulfide at temperatures above about 1100 F. to formmanganese sulfide, followed by oxidizing the manganese sulfide tomanganese oxide by reaction with oxygen, wherein undesired higher oxidesof manganese are formed, in said lastmentioned step the improvementwhich minimizes formation of said higher oxides, comprising introducinginto a regeneration zone maintained at a temperature from 1300 to 1800F. relative quantities of sulfided acceptors, combustible carbon, andoxygen so that only about 85 to 98 percent of the sulfided sulfur insaid sulfided acceptor is oxidized, withdrawing acceptor from saidregeneration zone containing 2 to 15 percent of its sulfide sulfur andcontaining a major portion of its manganese in the form of MnO, andrecovering the withdrawn acceptors as a stream for reuse under HS-absorbing conditions.

7. In the method for removing sulfur from particulate carbonizedcarbonaceous solids which comprises preparing an intimate admixture ofsaid carbonaceous solids and particulate acceptor solids comprisingmanganese oxide, subjecting said admixture to treatment at a temperatureabove 1100 F. in the presence of hydrogen gas until a portion of theinitial sulfur has been removed from said carbonaceous solids andtransferred to said acceptor solids thereby forming manganese sulfide,separating particulate acceptor solids containing manganese sulfide fromlow sulfur carbonaceous solids as product, and restoring the H 8absorbing property of sulfided acceptor solids for recirculation in theprocess, the improvement in said last-mentioned step comprisingintroducing into a regeneration zone maintained at a temperature from1300 to 1800 F. relative quantities of sulfided acceptor, combustiblecarbon, and oxygen so that only about 85 to 98 percent of the sulfidesulfur in said sulfided acceptor is oxidized, withdrawing acceptor fromsaid regeneration zone containing 2 to 15 percent of its sulfide sulfurand containing the major portion of its manganese in the form of MnO,and recovering the withdrawn acceptor as a stream for reuse under Hs-absorbing conditions.

References Cited in the file of this patent UNITED STATES PATENTS2,086,507 Carson July 6, 1937 2,764,528 Sweeney Sept. 25, 1956 2,824,047Gorin et a1. Feb. 18, 1958 2,950,230 Batchelor et al Aug. 23, 1960FOREIGN PATENTS 708,554 Great Britain May 5, 1954 519,283 Canada Dec. 6,1,955

1. IN A PROCESS EMPLOYING SOLID ACCEPTORS CONTAINING MANGANESE OXIDE FORABSORBING HYDROGEN SULFIDE AT TEMPERATURES ABOVE ABOUT 1100*F. TO FORMMANGANESE SULFIDE, FOLLOWED BY OXIDIZING THE MANGANESE SULFIDE TOMANGANESE OXIDE BY REACTION WITH OXYGEN, WHEREIN UNDESIRED HIGHER OXIDESBY REACTION WITH OXYGEN, WHEREIN UNDESIRED MENTIONED STEP THEIMPROVEMENT WHICH MINIMIZES FORMATION OF SAID HIGHER OXIDES, COMPRISINGCONTROLLABLY OXIDIZING ONLY ABOUT 85 TO 98 PERCENT OF THE SULFIDE SULFURIN SAID SULFIDE ACCEPTORS SO AS TO MAINTAIN ABOUT 2 TO 15 PERCENT OF THEMANGANESE IN THE FORM OF MNS, WHEREBY A MAJOR PORTION OF THE MANGANESEIS IN THE FORM OF MNO AND FORMATION OF HIGHER OXIDES OF MANGANESE INMINIMIZED, AND RECOVERING THE THUS-TREATED REGENERATED ACCEPTORS FORREUSE UNDER H2S-ABSORBING CONDITIONS.